Merge r1398970, r1407853, r1398480, r1398478, r1411862, r1397320:

    1398970: Use 'ap_strcasestr' instead of a strdup/str_tolower/strstr sequence
    1407853: cppCheck:  Suspicious condition.
    1398480: cppcheck: arrayIndexThenCheck - change the order of the tests in
             order to avoid a potential out-of-bound access.
    1398478: ccpcheck: duplicateExpression - 'vary_by_language' is tested twice
    1411862: Use apr_is_empty_table() instead of getting a table and checking the
             value of the 'nelts' field.
    1397320: remove extra ';'

Submitted by: jailletc36
Reviewed by: jailletc36, minfrin, sf


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1418945 13f79535-47bb-0310-9956-ffa450edef68